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Headshot of Emily Lakdawalla

A timeline for Dawn's launch

Posted by Emily Lakdawalla

02-07-2007 16:41 CDT


I'm waiting impatiently for the results of tomorrow's launch readiness review for the Dawn mission. I'm keeping my fingers crossed that they've gotten all those nagging problems solved and will be ready to go on Saturday, July 7.

They're certainly making progress preparing the spacecraft for launch. As I was checking the Kennedy Media Center just now they added a few more photos, showing the spacecraft and its upper stage motor being encased in the aerodynamic fairing that will enshroud them both for their journey up through Earth's atmosphere.

Dawn fairing encapsulation

NASA / Amanda Diller

Dawn fairing encapsulation
In the mobile service tower at launch pad 17-B at Cape Canaveral Air Force Station on July 1, 2007, the Dawn spacecraft (black cube) and Star 28 upper stage motor (white) are encased in the payload fairing of their Delta II launch vehicle.
In preparation for covering the launch events, I've distilled the time information from the mission's press kit and from Marc Rayman's last Dawn Journal into this table, which you might find handy if you plan to follow along. Stay tuned for more Dawn news!
Time (EDT)Time (UTC)
The launch window is about 27 minutes long. At liftoff, the first stage of the rocket and six of the nine solid rocket boosters ignite.
First six solid rocket boosters burn out
The first stage of the rocket is still firing as the six solids burn out at an altitude of 24 kilometers (15 miles).
Remaining three solid rocket boosters ignite0:02.01:19.016:10:5020:10:50
Burned-out solids separate
This happens as the first stage and three solids continue to fire. The separation of the six burned-out solids happens three at a time, with one second elapsing in between the separation events.
Remaining three solids burn out1:14.52:35.016:12:0620:12:06
Remaining solids separate
The last of the solid rocket boosters fall off as the rocket passes through an altitude of 73 kilometers (45 miles).
First stage shutoff1:43.54:23.016:13:5420:13:54
First stage separation0:08.04:31.016:14:0220:14:02
Second stage ignition0:05.04:36.016:14:0720:14:07
Payload fairing jettison
At an altitude of 135 kilometers (84 miles), the nose cone of the rocket splits in half and falls away, and the Dawn spacecraft is exposed to space for the first time.
Second stage shutdown
There is a pause in the middle of the firing of the second stage; the spacecraft coasts until it has reached exactly the right position in Earth orbit to begin the journey to Vesta via Mars.
Second stage restart9:07.018:05.016:27:3620:27:36
Second stage shutdown
The first and second stages have placed the spacecraft, still connected to the third and the spent second stage, into orbit at an altitude of 190 kilometers (118 miles).
Thrusters spin up the spacecraft to 50 revolutions per minute
The spacecraft is spun in order to stabilize it for its onward journey.
Second stage separation0:04.021:37.016:31:0820:31:08
Star 48 upper (third) stage ignition0:37.022:14.016:31:4520:31:45
Star 48 burnout
The third and final rocket stage burns out at an altitude of only 278 kilometers (173 miles) above Earth. For the rest of the mission, Dawn will depend upon ions for all further changes to its trajectory.
Spindown to zero
A yo-yo despin system will counteract the spacecraft's spin. However, the xenon in the tank will still be spinning. Friction will eventually slow it down, but not before it has imparted some spin to the spacecraft.
Third stage separation
The spent third stage falls away at an altitude of 1,016 kilometers (631 miles).
Thrusters counteract remaining spin
After waiting a little more than 8 minutes for the liquid xenon to swirl to a stop, the spacecraft's hydrazine attitude-control thrusters will counteract whatever spin the spacecraft gained from the process.

See other posts from July 2007


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